Move rateLimiterMiddleware to a separate file

src/middleware/rateLimitMiddleware.ts

@@ -0,0 +1,12 @@
+import { MiddlewareHandler } from '@hono/hono';
+import { rateLimiter } from 'hono-rate-limiter';
+
+/** Rate limit middleware for Hono. */
+export function rateLimitMiddleware(limit: number, windowMs: number): MiddlewareHandler {
+  return rateLimiter({
+    limit,
+    windowMs,
+    skip: (c) => !c.req.header('x-real-ip'),
+    keyGenerator: (c) => c.req.header('x-real-ip')!,
+  });
+}